A conventional check valve has a case where a fluid passage and a valve seat are formed, a valve member that touches and separates from the valve seat to open and close the fluid passage, and a spring that energizes the valve member in a valve-closing direction.
Further, the check valve is opened when an energization force of fluid in a valve opening direction exceeds an energization force of the spring in a valve closing direction (refer to Japanese Patent Application Laid-Open Publication No. 2001-50174, for example).
However, since an opposite side of the valve seat in the valve member serves as the fluid passage and the fluid flows along with the valve member in the conventional check valve, fluid force occurs parallel with a fluid flowing direction by the fluid flow during the check valve is opened (in other words, in a direction that the valve member reciprocates), thus the valve member easily hunts (i.e. undergoes oscillatory behavior of a non-converging feedback loop) in the valve member reciprocating direction.
Moreover, there is a problem that, due to the hunting of the valve member, pressure pulses occur, or noise occurs from apparatus and piping that vibrate due to the pressure pulses.